Overview
This lecture explains St. Thomas Aquinas's five proofs for the existence of God, as presented in his Summa Theologica, each rooted in observations of the natural world and influenced by Aristotle.
The Five Proofs of God's Existence
Argument from Motion
- Every object in motion was once at rest and moved by something else.
- This chain of movement cannot go back infinitely; there must be a First Mover.
- Aquinas calls this unmoved mover God.
Argument from Causation
- Everything in existence has an efficient cause or creator.
- An infinite chain of causes is impossible; there must be a First Cause.
- This First Cause, uncaused by anything else, is identified as God.
Argument from Contingency
- Possible beings can exist or not exist and are created/destroyed.
- If all beings were possible, there would be a time when nothing existed.
- For anything to exist now, there must be a Necessary Being that always exists—this is God.
Argument from Degrees of Perfection
- People compare things as more or less perfect, implying a standard of perfection.
- There must be an absolute standard or most perfect being.
- This perfectly good being, to which all perfection is compared, is God.
Argument from Final Causes (Design/Teleological Argument)
- All natural beings act towards purposes, showing evidence of design.
- The purposeful design of the world implies an intelligent Designer.
- This designer, more intelligent than humans, is God.
Key Terms & Definitions
- Unmoved Mover — The First Mover who causes motion without being moved (God).
- Efficient Cause — The direct cause of something’s existence or change.
- Necessary Being — A being that must exist and cannot not exist (God).
- Possible Being — A being that can exist or not exist.
- Final Cause — The purpose or end goal for which something exists.
- Degrees of Perfection — Comparative measurement of qualities that points to an ultimate standard.
Action Items / Next Steps
- Review the five proofs and understand their logical structure.
- Prepare examples or analogies for each argument.
- Read Summa Theologica sections on the existence of God for deeper understanding.